How many miles are on your car? What mods do you have? When was the last time it was tuned up? If you tuned it up recently, did you use Ford or a quality aftermarket (like Accel or MSD) products? Sometimes cheap iginition parts can wreak havoc on a car's performance. Does the car jerk when this happens or does it feel as if the engine is going to quit? Might want to check the free play in the distributor as well. Just my $.02 worth